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ID_MMFR5_EL1, AArch32 Memory Model Feature Register 5

The ID_MMFR5_EL1 characteristics are:

Purpose

Provides information about the implemented memory model and memory management support in AArch32 state.

For general information about the interpretation of the ID registers see 'Principles of the ID scheme for fields in ID registers' in the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile, section D10.4.1.

Configuration

AArch64 System register ID_MMFR5_EL1 bits [31:0] are architecturally mapped to AArch32 System register ID_MMFR5[31:0] .

This register is present only when AArch32 is supported at any Exception level. Otherwise, direct accesses to ID_MMFR5_EL1 are UNKNOWN.

Attributes

ID_MMFR5_EL1 is a 64-bit register.

Field descriptions

The ID_MMFR5_EL1 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
RES0
RES0ETS
313029282726252423222120191817161514131211109876543210

Bits [63:4]

Reserved, RES0.

ETS, bits [3:0]

Support for Enhanced Translation Synchronization. Defined values are:

ETSMeaning
0b0000

Enhanced Translation Synchronization is not supported.

0b0001

Enhanced Translation Synchronization is supported.

All other values are reserved.

ARMv8.0-ETS implements the functionality identified by the value 0b0001.

From Armv8.0, the permitted values are 0b0000 and 0b0001.

Accessing the ID_MMFR5_EL1

Accesses to this register use the following encodings:

MRS <Xt>, ID_MMFR5_EL1

op0op1CRnCRmop2
0b110b0000b00000b00110b110
if PSTATE.EL == EL0 then
    if IsFeatureImplemented("ARMv8.4-IDST") then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.SystemAccessTrap(EL2, 0x18);
        else
            AArch64.SystemAccessTrap(EL1, 0x18);
    else
        UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && (!IsZero(ID_MMFR5_EL1) || boolean IMPLEMENTATION_DEFINED "ID_MMFR5_EL1 trapped by HCR_EL2.TID3") && HCR_EL2.TID3 == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        return ID_MMFR5_EL1;
elsif PSTATE.EL == EL2 then
    return ID_MMFR5_EL1;
elsif PSTATE.EL == EL3 then
    return ID_MMFR5_EL1;